Automatic temperature control for refrigeration compressor motor

ABSTRACT

A sealed motor-compressor unit having a compressor discharge outlet connected to the interior of a motor casing by way of two parallel paths. A first path leads from the compressor discharge outlet directly to the interior of the motor casing, and a second path flows through a desuperheater. A bimetallic valve is placed adjacent the compressor discharge outlet, said valve being disposed to vary the opening to the path through the desuperheater in accordance with the temperature of the gas discharged from the compressor so as to vary the amount of desuperheated gas delivered to the motor casing and to provide automatic temperature control for the compressor motor.

United States Patent 1 1 1 1 3,727,420

Kosfeld 51 Apr. 17, 1973 AUTOMATIC TEMPERATURE 3,396,550 8/1968 Czwley ..62/505 I CONTROL FOR REFRIGERATION COMPRESSOR M T Primary Examiner-Meyer Perlin h a .9 ,1 An -D 'd S. Kan t al. [75] Inventor: Milton M. Kosfeld, North Brunsomey a v e e 57 ABSTRACT [73] Assignee: Fedders Corporation, Edison, N]. A Sealed motor-compressor unit having a compressor discharge outlet connected to the interior of a motor Flledl 1971 casing by way of two parallel paths. A first path leads [21] APP] No; 177,187 from the compressor discharge outlet directly to the interior of the motor casing, and a second path flows through a desuperheater. A bimetallic valve is placed [52] US. Cl ..62/ 196, 62/505 dj ent the compressor discharge outlet, Said valve [51 Ilit. CI ..F25b 41/00 being di posed to vary the opening to the path through Field of Search-m the desuperheater in accordance with the temperature 417/369 of the gas discharged from the compressor so as to vary the amount of desuperhea'ted gas delivered to the References Cited motor casing and to provide automatic temperature UNITED STATES PATENTS control for the compressor motor.

2,979,917 4/1961 Meagher 62/505 8 Claim 4 Drawing Figures 3,302,424 2/1967 Schenzinger ..62/505 PATENTEDAFR 1 H1115 3.727, 420

I F/G. 2

AUTOMATIC CONTROL FOR REFRIGERATION COMPRESSOR MOTOR BACKGROUND OF THE INVENTION 1 Field of the Invention The present invention relates to refrigeration compressors and more particularly to an apparatus for automatically controlling the motor temperature of a motor compressor unit.

2. Description of the Prior Art When using a hermetically sealed motor-compressor combination unit in a refrigeration system, it is essential that the compressor motor be cooled during system operation. It has become common in the refrigeration art to pass the hot discharge gas from the compressor through a precooling or desuperheat coil to remove excessive heat from the gas and then to direct the desuperheated gas into the motor case to cool the motor prior to passing the gas into the condenser of the refrigeration system.

To prevent overheating the motor and shortening its life, the desuperheater coil must be adequately sized for high ambient temperature. At low ambient temperature excessive cooling will occur, condensing refrigerant into the compressor case. This condensed refrigerant mixes with the lubricating oil critically shortening bearing life.

In a prior art device taught in U. S. Pat. No. 2,979,917 issued to G. L. Meagher, a valve is located in a conduit, which passes through a desuperheater and connects a compressor discharge outlet with the motor casing, said valve is controlled by a temperature sensing element located within the motor casing. A second conduit leads directly from they compressor discharge outlet to the motor casing and has a pressure controlled valve positioned therein. When the temperature in the motor casing drops below a specified level, the valve in the desuperheater conduit closes causing a back pressure at the discharge outlet of the compressor, which acts on the pressure sensitive valve in the direct conduit causing said valve to open and pass gas directly to the motor casing without passing through the desuperheater.

The above-prescribed device requires two separate valves and a temperature sensor, which adds to the cost and complexity of the overall unit and requires periodic maintenance.

SUMMARY OF THE INVENTION The present invention contemplates a hennetically sealed motor-compressor unit having two parallel paths between a compressor discharge outlet and a motor casing for passing discharged gas from the compressor to the motor for purposes of cooling the motor. A first path between the compressor outlet and motor casing is a direct and unobstructed path while the second path leads through a desuperheater and includes a temperature sensitive bimetallic valve to vary the opening to the second path. The bimetallic valve is located adjacent the discharge outlet of the compressor and is responsive to compressor discharge gas temperature to vary the opening to the path to the desuperheater and thereby vary the amount of desuperheated gas delivered to the motor.

The valve is inexpensively manufactured by stamping a disc shape from bimetallic material. The valve is positioned within the compressor so that when it bends in one direction asa result of low temperature exposure, it closes the opening to the second path and when it is exposed to a higher temperature, the disc bends in an opposite direction opening the path.

It has been determined that the use of two parallel paths when desuperheating is required provides adequate cooling for the motor while the bimetallic valve protects the motor from the detrimental effects of excessive cooling when desuperheating is not required. The bimetallic valve is almost maintenance free and is easy to manufacture from inexpensive material. Positioning of the valve adjacent the discharge outlet of the compressor eliminates the need for a separate temperature sensor in the motor housing and the need for a connection between the sensor and the valve. A separate pressure responsive valve is not required because adequate cooling is provided by the use of parallel paths connecting the compressor and motor casing. It has also been determined that adequate motor temperature control may be realized by sensing the temperature of the compressor discharged gas, and it is not necessary to sense the temperature in the motor case itself.

Thus, the present invention provides an automatic temperature control for the motor of a motor-compressor unit that is as effective as the temperature controls heretofore provided; however, the device taught by the present invention is less expensive and less complicated than the devices of the prior art. The device is inexpensively manufactured and requires practically no maintenance.

The primary objective of the present invention is to provide an automatic temperature control for the motor of a motor-compressor unit.

Another objective of the present invention is to provide an automatic temperature control that requires less maintenance than the controls heretofore provided.

Another objective of the present invention is to provide an automatic temperature control that is less expensive than the devices heretofore provided.

Another objective of the present invention is to provide an inexpensive, bimetallic valve for controlling temperature in a motor-compressor unit.

The foregoing objectives and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken with the accompanying drawing, wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for illustrative purposes only and is not to be considered as defining the limits of the invention.

DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of a motor-compressor unit constructed in accordance with the present invention.

FIG. 2 is a plan view of a bimetallic valve used in the embodiment shown in FIG. 1.

FIG. 3 is an edge view of the bimetallic valve of FIG. 2 shown exposed to a low temperature.

FIG. 4 is an edge view of the bimetallic valve of FIG. 2 shown exposed to a high temperature.

DESCRIPTION OF THE INVENTION Referring to FIG. 1, there is shown a motor-compressor unit generally designated as 10. Unit is hermetically sealed in a manner well known in the art and could be utilized in a reversible refrigeration system. Hermetic casing 12 encloses a compressor 14 and a I motor 16, which are separated by a partition 18, which divides casing 12 into two chambers; namely, a motor chamber and a compressor chamber 22. Compressor 14 has an annular compression chamber 24 disposed within a cylindrical housing 26. A drive shaft 28 is mounted in a bearing 30 disposed in the center of partition 18 to is drivably connected to an eccentric 32, which drives a rotor 34 positioned off center within the annular compression chamber 24. Partition 18 serves as an upper wall of the annular compression chamber and an end plate 36 provides a bottom wall. Thus, rotor 34 disposed within the annular compression chamber 24 and driven by eccentric 32 forms a rotary compressor of a type well known in the art. A reciprocating blade (not shown) is disposed within a slot formed in cylindrical housing 26 and wipes against the face of the rotor during its rotation within the compressor chamber ot divide the chamber into high and low pressure sides. The construction and details of this blade need not be shown in this specification as they are well known in the art.

End plate 36 has an opening 38 formed therein for receiving a conduit 40, which provides low pressure refrigerant gas to the compressor 14. Rotor 34 functions as an inlet valve to periodically connect conduit 40 to the low pressure side of the annular compression chamber 24 and to prevent reverse flow of refrigerant gas into conduit 40. FIG. 1 is a cross section taken through the high pressure side of annular compression chamber 24 and shows rotor 34 closing the inlet from conduit 40.

High pressure gas from annular compression chamber 24 is expelled through an opening 42 formed in cylinder wall 26 and into discharge chamber 44. Mounted within the discharge chamber 44 is a valve 46 constructed in a manner well known in the art and including a valve 'backer 48. Valve backer 48 has openings 50 formed therein for the passage of gas therethrough.

Drive motor 16 has a stator element 52 mounted to the interior of casing 12 and a rotor element 54 mounted to drive shaft 28, which extends into motor chamber 20. Thus, motor 16 functions to rotate rotor 34, which compresses the low pressure refrigerant gas received from conduit 40.

A passage 56 is formed in partition 18 for connecting discharge 44 with the motor chamber 20 so that compressedrefrigerant gas may flow into motor chamber 20. An output conduit 58 communicates with motor' chamber 20 to provide compressed refrigerant gas to a heat exchanger in a refrigeration system.

When the motor-compressor unit is connected in a system .that is operating as an air conditioner, the discharge gas from the compressor discharge chamber 44 is at a high temperature and does not provide sufficient cooling for the motor. Therefore, a desuperheater 60 in the form of a heat removing coil normally exposed to outdoor air is connected in the system to receive a portion of the high pressure discharge refrigerant gas through a conduit 62, which is connected to the discharge chamber 44 by way of a valve mounting chamber 64. The desuperheater has an output connected to the motor chamber 20 by way of conduit 66. Thus, parallel flow paths are provided for the hot discharge'refrigerant gas, one path through passage 56 and the other path through conduit 62, desuperheater and conduit 66. Desuperheater 60 sufficiently desuperheats enough high pressure discharge gas so that motor 16 is cooled to a safe operating temperature. A small amount of refrigerant gas flowing through the desuperheater may liquefy; however, this gas is immediately carried through the desuperheater ture operation, the system is used to provide heat and in such cases the refrigerant gas provided by conduit 40 is at a low temperature that is detrimental to motor 16. The gas temperature increases as the gas is compressed in compressor 14, however, if the gas is passed through desuperheater 60, the temperature would again be reduced to a level that would adversely affect the lubrication of bearing 30 and would lead to decreased motor life. The use of desuperheater 60 during low ambient temperature operation would also greatlydecrease the system efficiency by removing heat in the outdoor heat exchanger rather than providing it to the indoor air where heating is desired. Thus, a means is required to eliminate the desuperheater 60 from the system during low ambient temperature operation.

A bimetallic valve 68 is mounted within valve mounting chamber 64 and is positioned adjacentto the opening to conduit 62. Valve 68 is formed of a bimetal and is generally disc shaped having two end tabs as shown in FIG. 2. The valve may be inexpensively-manufactured by stamping from standard bimetal stock. Valve 68 is positioned within chamber 64 so that when the valve is subjected to a predetermined low temperature, it bends in a direction as shown in FIGS. 1 and 3 to close the opening to conduit 62 and prevent discharge gas from entering desuperheater 60. When the tern.- perature of the discharge gas increases to a predetermined high temperature, the valve bends in a direction as shown in FIG. 4, thereby fully opening the entrance to conduit 62 and allowing a maximum amount of gas to pass to desuperheater 60 for maximum cooling.

Thus, the present invention provides an automatic temperature control for the motor of a motor-compressor unit. The temperature is automatically controlled by a single bimetallic valve, which senses the temperature of the refrigerant gas discharged from the compressor and in response thereto varies the opening to a conduit flowing to a desuperheater. The valve is selfcontrolled and therefore essentially maintenance free resulting in reduced maintenance cost. Because of the valves simplicity, it is easy to manufacture from inexpensive material resulting a cost reduction in the overall motor-compressor unit.

What is claimed is:

l. A refrigeration motor-compressor unit having an automatic motor temperature control, comprising:

a refrigerant gas compressor having a low pressure inlet and a high pressure outlet;

a motor drivably connected to said compressor;

a casing for said motor having gas inlet and outlet means;

a source of low pressure refrigerant gas connected to the inlet of the compressor;

a conduit connecting the compressor outlet to the inlet means in the motor casing for supplying high pressure gas for cooling the motor;

a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the motor casing inlet means for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the motor casing for cooling the motor; and

valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet and positioned adjacent the compressor outlet for varying the flow of discharge gas to the desuperheating coil, whereby the size of the portion of high pressure refrigerant discharge gas supplied to the desuperheater and ultimately supplied to the motor casing is controlled.

2. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising:

a hermetically sealed case;

a compressor mounted in said case having a low pressure inlet and a high pressure outlet;

a motor mounted in said case and drivably connected to said compressor;

a source of low pressure refrigerant gas connected to the inlet of the compressor;

an outlet formed in said case for delivering high pressure refrigerant gas to a refrigerant system;

a conduit connected to the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein;

a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and

valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet for closing said desuperheating coil when the gas temperature falls below a predetermined temperature.

3. A refrigeration compressor as described in Claim 2, wherein the compressor outlet includes a discharge chamber to which the conduit and desuperheating coil inlet are connected.

4. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising:

a hermetically sealed case;

a compressor mounted in said case having a low pressure inlet and a high pressure outlet;

a motor mounted in said case and drivably connected to said compressor;

a source of low pressure refrigerant gas connected to the inlet of the compressor;

an outlet formed in said case for delivering high pressure refrigerant gas to a refrigeration system;

a conduit connected to the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein;

a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and

valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet for closing said desuperheating coil when the gas temperature falls below a predetermined temperature, said valve means being positioned within the compressor and adjacent the inlet of the desuperheating coil.

5. The hermetically sealed refrigeration compressor having automatic motor temperature control, comprising:

a hermetically sealed case; a compressor mounted in said case having a low pressure inlet and a high pressure outlet including a discharge chamber;

a motor mounted in said case and drivably connected to said compressor;

a source of low pressure refrigerant gas connected to the inlet of the compressor;

an outlet formed in said case for delivering high pressure refrigerant gas to a refrigeration system;

a conduit connected to the discharge chamber of the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein;

a desuperheating coil having an inlet connected to the discharge chamber of a compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and

valve means disposed within the discharge chamber and positioned adjacent the inlet of the desuperheating coil, said valve means responsive to the temperature of the high pressure refrigerant discharge gas in the discharge chamber for closing said desuperheating coil when the gas temperature falls below a predetermined temperature.

6. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising:

a hermetically sealed case;

a compressor mounted in said case having a low pressure inlet and a high pressure outlet;

a motor mounted in said case and drivably connected to said compressor;

a source of low pressure refrigerant gas connected to the'inlet of the compressor;

, an outlet formed in said case for delivering high presof the high pressure refrigerant discharge gas for closing the inlet when subjected to a predetermined temperature.

7. A refrigeration compressor as described in claim v6, wherein the compressor outlet includes a discharge chamber and the bimetallic valve is mounted therein and positioned to close the desuperheater inlet at a predetermined refrigerant gas discharge temperature.

8. A refrigeration compressor as described in claim 7, wherein the bimetallic valve is disc shaped having a pair of tabs positioned opposite each other, said tabs engaging walls forming the discharged chamber. 

1. A refrigeration motor-compressor unit having an automatic motor temperature control, comprising: a refrigerant gas compressor having a low pressure inlet and a high pressure outlet; a motor drivably connected to said compressor; a casing for said motor having gas inlet and outlet means; a source of low pressure refrigerant gas connected to the inlet of the compressor; a conduit connecting the compressor outlet to the inlet means in the motor casing for supplying high pressure gas for cooling the motor; a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the motor casing inlet means for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the motor casing for cooling the motor; and valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet and positioned adjacent the compressor outlet for varying the flow of discharge gas to the desuperheating coil, whereby the size of the portion of high pressure refrigerant discharge gas supplied to the desuperheater and ultimately supplied to the motor casing is controlled.
 2. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising: a hermetically sealed case; a compressor mounted in said case having a low pressure inlet and a high pressure outlet; a motor mounted in said case and drivably connected to said compressor; a source of low pressure refrigerant gas connected to the inlet of the compressor; an outlet formed in said case for delivering high pressure refrigerant gas to a refrigerant system; a conduit connected to the compressor outlet for discharging high pressure gas from the compressor into the case for coolIng the motor mounted therein; a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet for closing said desuperheating coil when the gas temperature falls below a predetermined temperature.
 3. A refrigeration compressor as described in Claim 2, wherein the compressor outlet includes a discharge chamber to which the conduit and desuperheating coil inlet are connected.
 4. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising: a hermetically sealed case; a compressor mounted in said case having a low pressure inlet and a high pressure outlet; a motor mounted in said case and drivably connected to said compressor; a source of low pressure refrigerant gas connected to the inlet of the compressor; an outlet formed in said case for delivering high pressure refrigerant gas to a refrigeration system; a conduit connected to the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein; a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and valve means responsive to the temperature of the high pressure refrigerant discharge gas at the compressor outlet for closing said desuperheating coil when the gas temperature falls below a predetermined temperature, said valve means being positioned within the compressor and adjacent the inlet of the desuperheating coil.
 5. The hermetically sealed refrigeration compressor having automatic motor temperature control, comprising: a hermetically sealed case; a compressor mounted in said case having a low pressure inlet and a high pressure outlet including a discharge chamber; a motor mounted in said case and drivably connected to said compressor; a source of low pressure refrigerant gas connected to the inlet of the compressor; an outlet formed in said case for delivering high pressure refrigerant gas to a refrigeration system; a conduit connected to the discharge chamber of the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein; a desuperheating coil having an inlet connected to the discharge chamber of a compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and valve means disposed within the discharge chamber and positioned adjacent the inlet of the desuperheating coil, said valve means responsive to the temperature of the high pressure refrigerant discharge gas in the discharge chamber for closing said desuperheating coil when the gas temperature falls below a predetermined temperature.
 6. A hermetically sealed refrigeration compressor having automatic motor temperature control, comprising: a hermetically sealed case; a compressor mounted in said case having a low pressure inlet and a high pressure outlet; a motor mounted in said case and drivably connected to said compressor; a source of low pressure refrigerant gas connected to the inlet of the compressor; an outlet formed in said case for delivering high pressure refrigerant gas to a refrigeration system; a conduit connected to the compressor outlet for discharging high pressure gas from the compressor into the case for cooling the motor mounted therein; a desuperheating coil having an inlet connected to the compressor outlet and an outlet connected to the case for desuperheating a portion of the high pressure refrigerant gas discharged by the compressor and for supplying said desuperheated gas to the case for cooling the motor; and a bimetallic valve disposed adjacent the inlet to desuperheating coil and responsive to the temperature of the high pressure refrigerant discharge gas for closing the inlet when subjected to a predetermined temperature.
 7. A refrigeration compressor as described in claim 6, wherein the compressor outlet includes a discharge chamber and the bimetallic valve is mounted therein and positioned to close the desuperheater inlet at a predetermined refrigerant gas discharge temperature.
 8. A refrigeration compressor as described in claim 7, wherein the bimetallic valve is disc shaped having a pair of tabs positioned opposite each other, said tabs engaging walls forming the discharged chamber. 